JP6023672B2 - Image forming apparatus - Google Patents

Description

  The present invention relates to an image forming apparatus.

  2. Description of the Related Art Conventionally, as an electrophotographic image forming apparatus, a toner image carried on a peripheral surface of a photosensitive roller is transferred onto the sheet by sandwiching the sheet between a photosensitive roller (drive roller) and a transfer roller. Things are known. A transfer roller gear is integrally connected to one end of the transfer roller, and a gear (drive roller gear) meshing with the transfer roller gear is integrally connected to one end of the photosensitive roller. The transfer roller is biased toward the photosensitive roller by an elastic member.

  In addition, a toner image carried on the peripheral surface of the photosensitive roller is first temporarily transferred to a transfer belt and then secondarily transferred to a sheet (for example, see Patent Document 1).

  In this apparatus, a transfer belt is sandwiched between a photosensitive roller (driving roller) and a primary transfer roller, whereby the toner image carried on the peripheral surface of the photosensitive roller is primarily transferred to the transfer belt.

  The transfer belt is driven by a belt support roller provided on the inner peripheral side thereof. Then, the toner image on the transfer belt is transferred onto the sheet by sandwiching the sheet with the transfer belt between the belt support roller (drive roller) and the secondary transfer roller. A transfer roller gear is rotatably connected to one end of the secondary transfer roller, and a gear (drive roller gear) that meshes with the transfer roller gear is connected to the one end of the belt support roller. ing. The secondary transfer roller is biased toward the belt driving roller by an elastic member.

JP 2007-193000 A

  However, in the conventional image forming apparatus, the transfer roller is urged toward the driving roller by an elastic member, and is movable in this urging direction. For this reason, when the transfer roller gear receives a gear reaction force in a direction away from the drive roller gear, the transfer roller may be displaced in a direction away from the drive roller. As a result, there is a problem in that the toner transfer pressure acting on the transfer target from the transfer roller escapes to cause transfer failure, or rotation of the transfer roller is hindered due to poor meshing between both gears.

  The present invention has been made in view of such a point, and the object of the present invention is to cause the transfer roller to be a drive roller due to a gear reaction force that the transfer roller gear receives when the drive roller gear is rotationally driven. It is to prevent separation from.

The image forming apparatus according to the present invention includes a driving source, thereby transferring a photoreceptor roller is a drive roller that is rotationally driven by the driving source, the toner image carried on the outer peripheral surface of the photoconductor roller to the intermediate transfer belt a transfer roller, and an elastic member for urging the transcription roller above Symbol photoconductor roller side, a drive roller gear coupled to rotate together on Stories photoconductor roller, transfer coupled to rotate integrally with the transfer roller And a roller gear.

The direction of the force acting on the transfer roller from the elastic member is determined along the straight line passing through the axis of the transfer roller gear and the axis of the drive roller gear when viewed from the axial direction of the transfer roller. The direction is from the transfer roller side to the photosensitive roller side, and the driving force of the drive roller gear is transmitted to the transfer roller gear so that the drive roller gear and the transfer roller gear rotate in directions opposite to each other. A plurality of idle gears provided with an even number
The plurality of idle gears includes a first idle gear that meshes with the transfer roller gear and a second idle gear that meshes with the drive roller gear, and the transfer gear as viewed from the axial direction of the transfer roller. The common normal at the contact point between the tooth surface of the roller gear and the tooth surface of the first idle gear is parallel to the straight line, so that the first idle gear acts on the transfer roller gear. The direction of the force is configured to match the direction of the force that the transfer roller receives from the elastic member.

According to this configuration, the direction of the force that acts on the transfer roller gear from the first idle gear is made to coincide with the direction of the force that the transfer roller receives from the elastic member, that is, the direction that urges the transfer roller toward the drive roller. Therefore, it is possible to prevent the transfer roller gear from being displaced in the direction away from the drive roller gear due to the gear reaction force. Accordingly, it is possible to prevent the toner transfer pressure that acts on the intermediate transfer belt from the transfer roller from escaping and causing a transfer failure, or the rotation of the transfer roller from being hindered by a gear meshing failure.

  According to the present invention, it is possible to prevent the transfer roller from being separated from the drive roller due to the gear reaction force received by the transfer roller gear when the drive roller gear is rotationally driven.

FIG. 1 is a schematic cross-sectional view illustrating an image forming apparatus according to an embodiment. FIG. 2 is a side view showing a driving mechanism of the transfer roller as seen from a direction orthogonal to the axial direction of the roller. FIG. 3 is a side view showing the driving mechanism of the transfer roller as seen from the axial direction of the roller. FIG. 4 is a view corresponding to FIG. FIG. 5 is a view corresponding to FIG. 1 showing a reference embodiment.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. The present invention is not limited to the following embodiment.

Embodiment 1
-Overall configuration-
FIG. 1 shows a laser printer 1 (hereinafter simply referred to as a printer) as an image forming apparatus in the present embodiment. The printer 1 includes a housing 2, a paper feeding unit 10, an image forming unit 20, a primary transfer unit 30, a secondary transfer unit 40, and a fixing unit 50.

  The paper feeding unit 10 is disposed in the lower part of the housing 2. The paper feed unit 10 includes a paper feed cassette 11 in which sheet-like paper P is accommodated, and a pickup roller 12 for taking out the paper P in the paper feed cassette 11 and sending it out of the cassette. The paper P sent out of the cassette from the paper feed cassette 11 is supplied to the secondary transfer unit 40. In the secondary transfer unit 40, the toner image on the intermediate transfer belt 31 is transferred onto the paper P as described later.

  The image forming unit 20 includes four image forming units 21 and four optical scanning devices 26 provided for each unit 21. Each image forming unit 21 forms a yellow (Y), magenta (M), cyan (C), or black (K) toner image. Specifically, each image forming unit 21 includes a photosensitive roller 22, a charging device 23, a developing device 24, a cleaning device 25, and the like. Each optical scanning device 26 irradiates the peripheral surface of the photosensitive roller 22 with laser light based on predetermined image data. In each image forming unit 21, the developing device 24 develops the electrostatic latent image on the peripheral surface of each photoconductor roller 22 formed by laser light irradiation by the optical scanning device 26, so that the circumference of each photoconductor roller 22 is developed. A toner image of each color is formed on the surface. The toner image thus formed is primarily transferred to the intermediate transfer belt 31 by the primary transfer unit 30.

  The primary transfer unit 30 includes an intermediate transfer belt 31 wound around belt support rollers 32L and 32R and an idle roller 33 arranged in the left-right direction in FIG. 1, and four primary transfer rollers 34 arranged along the intermediate transfer belt 31. Have. The belt support roller 32L is rotationally driven via the intermediate transfer belt 31 by a motor (not shown). Each primary transfer roller 34 is disposed on the upper side of each photoconductor roller 22 with the intermediate transfer belt 31 interposed therebetween. Each primary transfer roller 34 is urged toward the photosensitive roller 22 by a compression spring 107 as an elastic member. A transfer bias is applied to each primary transfer roller 34 from a bias power source (not shown), and the intermediate transfer belt 31 is nipped and conveyed by each primary transfer roller 34 and each photoconductor roller 22, so that the photoconductor roller. The toner image on the peripheral surface 22 is transferred to the outer peripheral surface of the intermediate transfer belt 31.

  The secondary transfer unit 40 has a secondary transfer roller 41 disposed on the left side of the intermediate transfer belt 31 adjacent to the belt support roller 32L. The secondary transfer roller 41 is urged toward the belt support roller 32 </ b> L by the compression spring 42. A transfer bias is applied to the secondary transfer roller 41 from a bias power source (not shown), and the sheet P is nipped and conveyed together with the intermediate transfer belt 31 by the secondary transfer roller 41 and the belt support roller 32L. The toner image on the outer peripheral surface of the belt 7 is transferred to the paper P.

  The fixing unit 50 includes a heating roller 51 and a pressure roller 52 that rotate. The fixing unit 50 fixes the toner image transferred to the paper P by heating and pressing the paper P by nipping and conveying the paper P by the heating roller 51 and the pressure roller 52. The paper P on which the toner image is fixed by the fixing unit 50 is sent out downstream by the rollers 51 and 52.

  The paper discharge unit 60 is formed by denting the upper surface of the housing 2 downward, and the paper P sent out from the fixing unit 50 is discharged to the paper discharge unit 60 via the discharge roller 61.

-Primary transfer roller drive mechanism-
Next, the drive mechanism 100 of the primary transfer roller 34 will be described with reference to FIGS. 2 and 3. In FIG. 2, white arrows indicate the direction of force application, and black arrows indicate the rotation directions of the gears 101 to 104. This also applies to FIG. 4 showing the conventional example.

  The driving mechanism 100 includes a photosensitive roller gear 101 that is connected to the photosensitive roller 22 in a rotationally integrated manner, a transfer roller gear 102 that is connected to the primary transfer roller 34 in a rotationally integrated manner, and interposed between the roller gears 101 and 102. A first idle gear 103 and a second idle gear 104.

  As shown in FIG. 2, the photoconductor roller 22 includes a metal cylinder 22a whose both ends in the axial direction are closed, and a photosensitive layer 22b formed over the entire outer peripheral surface of the cylinder 22a. And a shaft 22c penetrating the axial center portion of the cylindrical body 22a. The shaft 22c is connected to the cylindrical body 22a so as to rotate together. The shaft 22c is connected to a motor (not shown) as a drive source via a power transmission mechanism including, for example, a belt and a gear. Thus, the photosensitive roller 22 is rotationally driven by a motor.

  Both ends of the shaft 22c are rotatably supported by a pair of bearings 105a and 105b (see FIG. 3). The photosensitive roller gear 101 is disposed outside the bearing 105a in the axial direction of the shaft 22c, and is connected to one end of the shaft 22c so as to rotate together.

  The primary transfer roller 34 has a metal shaft 34a and a semiconductive elastic layer 34b formed on the peripheral surface of the shaft 34a. Both end portions of the shaft 34a are rotatably supported by a pair of bearings 106a and 106b. Each of the bearings 106 a and 106 b is supported so as to be slidable in the vertical direction with respect to the housing 2, and is urged toward the photosensitive roller 22 by the compression spring 107. Thus, the primary transfer roller 34 is urged toward the photosensitive roller 22 by the compression spring 107 via the bearings 106a and 106b. The transfer roller gear 102 is disposed outside the bearing 106a in the axial direction of the shaft 34a, and is coupled to the shaft 34a so as to be integrally rotated.

  The first idle gear 103 is rotatably supported by a fixed shaft 108 fixed to the housing 2. The first idle gear 103 meshes with the transfer roller gear 102 and the second idle gear 104. The second idle gear 104 is rotatably supported by a fixed shaft 109 fixed to the housing 2. The second idle gear 104 meshes with the photosensitive roller gear 101 and the first idle gear 103. In the present embodiment, the number of teeth of the photosensitive roller gear 101, the transfer roller gear 102, the first idle gear 103, and the second idle gear 104 is 20, 15 teeth, 30 teeth, and 30 teeth, respectively. In this embodiment, the ratio of the number of teeth of the transfer roller gear 102 to the number of teeth of the photosensitive roller gear 101 is different from the ratio of the diameter of the primary transfer roller 34 to the diameter of the photosensitive roller 22.

  A common normal N (see FIG. 2) at the contact point between the tooth surface of the transfer roller gear 102 and the tooth surface of the first idle gear 103 is viewed from the axial direction of the primary transfer roller 34. The relationship is parallel to a straight line L passing through the axis and the axis of the photosensitive roller gear 101. The direction of the force acting on the transfer roller gear 102 from the first idle gear 103 is the direction from the primary transfer roller 34 side toward the photosensitive roller 22 side along the common normal line N. The direction of the force acting on the primary transfer roller 34 from the compression spring 107 is a direction along the straight line L from the transfer roller 34 side toward the photosensitive roller 22 side. That is, the direction of the force that acts on the transfer roller gear 102 from the first idle gear 103 matches the direction of the force that the primary transfer roller 34 receives from the compression spring 107.

  The operation and effect of the printer 1 configured as described above will be described in comparison with a conventional example. That is, in the printer 1 according to the conventional example, as shown in FIG. 4, the idler gears 103 and 104 are not interposed between the photosensitive roller gear 101 and the transfer roller gear 102, and the photosensitive roller gear 101 is transferred. It meshed directly with the roller gear 102. For this reason, the gear reaction force that acts on the transfer roller gear 102 from the photoconductor roller gear 101 always includes a component in a direction that separates the photoconductor roller gear 101 from the transfer roller gear 102. Therefore, when the photosensitive roller gear 101 is rotationally driven, the transfer roller gear 102 is displaced in a direction away from the photosensitive roller gear 101, and the transfer pressure of the toner acting on the intermediate transfer belt 31 from the primary transfer roller 34. Had the problem of running away.

  On the other hand, in the printer 1 according to the first embodiment, as described above, the first and second idle gears 103 and 104 are interposed between the photosensitive roller gear 101 and the transfer roller gear 102, and the first idle gear 103. The direction of the force acting on the transfer roller gear 102 is made to coincide with the direction of the force that the primary transfer roller 34 receives from the compression spring 107.

  Accordingly, it is possible to prevent the transfer roller gear 102 from being displaced in a direction away from the photosensitive roller gear 101 due to the gear reaction force when the photosensitive roller gear 101 is rotationally driven. Therefore, the toner transfer pressure acting on the intermediate transfer belt 31 that is the transfer target from the transfer roller 34 escapes to cause a transfer failure, and the rotation of the transfer roller 34 is prevented from being hindered by a gear meshing failure. Can do.

  Further, by providing the idler gears 103 and 104 between the photosensitive roller gear 101 and the transfer roller gear 102, the degree of freedom in designing both the roller gears 101 and 102 can be increased. That is, in the printer 1 according to the conventional example, if the ratio of the number of teeth of the two gears 101 and 102 does not match the diameter ratio of the two rollers 22 and 34, the surfaces of the two rollers 22 and 34 are caused by the difference in peripheral speed. There was a problem of slipping. On the other hand, in the above embodiment, by providing the idle gears 103 and 104, the ratio of the number of teeth of the transfer roller gear 102 to the number of teeth of the photoconductor roller gear 101 is changed to the transfer roller 34 with respect to the diameter of the photoconductor roller 22. Can be freely set without matching the diameter ratio.

<< Other embodiments >>
In the above embodiment, the two idle gears 103 and 104 are interposed between the photosensitive roller gear 101 and the transfer roller gear 102, but the number of idle gears is not limited to two. For example, it may be four or more. However, since the photosensitive roller gear 101 and the transfer roller gear 102 need to rotate in opposite directions, the number of idle gears is preferably an even number.

《Reference form》
Next, a reference form will be described. In this reference embodiment, as shown in FIG. 5, the drive mechanism 200 having the same configuration as the drive mechanism 100 so that used for driving of the secondary transfer roller 41. The configuration of the driving mechanism 200 replaces the photoconductor roller 22 in the drive mechanism 100 to the belt support rollers 32L, is similar to the structure obtained by replacing the primary transfer roller 34 to the secondary transfer roller 41. In this case, the belt support roller gear 201 constitutes a driving roller gear, the paper P constitutes a transfer medium, and the compression spring 42 constitutes an elastic member .

  As described above, the present invention is useful for an image forming apparatus, and particularly useful for an image forming apparatus having a transfer roller biased by an elastic member.

L straight line
N common normal 1 Laser printer (image forming equipment)
22 Photosensitive roller (drive roller)
31 Intermediate transfer belt 34 Primary transfer roller 41 Secondary transfer roller 42 Compression spring (elastic member)
101 Photosensitive roller gear (drive roller gear)
102 Transfer roller gear
103 first idle gear 104 second idle gear 107 compression spring (elastic member)

Claims (2)

Upper and driving source, a photoconductor roller is a drive roller that is rotationally driven by the driving source, and a transfer roller for transferring the toner image carried on the outer peripheral surface of the photoconductor roller to the intermediate transfer belt, a transcription roller an elastic member for urging the serial photoconductor roller side, a drive roller gear coupled to rotate together on Stories photoconductor roller, image formation and a transfer roller gear coupled to rotate together with the transfer roller A device,
The direction of the force acting on the transfer roller from the elastic member is the transfer roller along a straight line passing through the axis of the transfer roller gear and the axis of the drive roller gear as viewed from the axial direction of the transfer roller. Direction from the side toward the photosensitive roller side,
The drive force of the drive roller gear is transmitted to the transfer roller gear , and the drive roller gear and the transfer roller gear include a plurality of idle gears provided in an even number so as to rotate in opposite directions ,
The plurality of idle gears includes a first idle gear that meshes with the transfer roller gear and a second idle gear that meshes with the drive roller gear, and the transfer gear as viewed from the axial direction of the transfer roller. The common normal at the contact point between the tooth surface of the roller gear and the tooth surface of the first idle gear is parallel to the straight line, so that the first idle gear acts on the transfer roller gear. An image forming apparatus configured to match the direction of force with the direction of force received by the transfer roller from the elastic member. The image forming apparatus according to claim 1.
Number of teeth ratio of the transfer roller gear for the number of teeth of the driving roller gear is different from the ratio of the transfer roller diameter to the diameter of the upper Symbol photoconductor roller, an image forming apparatus.

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